Microscopic life-forms on Mars or on any of the other planets [and satellites of planets] of our Solar System,might have silicon or some other element as their basic molecular building block. Organic living life on Earth is based on carbon.

We already have variants of life on this planet such as the Octopus which uses copper in its blood instead of iron. I can see little reason to think that other more different variations should not be found elsewhere.

I could also be sarcastic and suggest that certain elements of the human race (teenagers) may be considered a sub-species also :-))

If microscopic life forms are found to exist (or to have existed in the past) on Mars there will of course be a great deal of excitement in the scientific community. There will also be a fresh crop of 'there must be other life forms out there' threads in this forum.

Apart from that, life here on earth will go on as usual.

The chances that some form of life existed before Mars lost its atmosphere are pretty high, I imagine, although I don't think there will be traces of ancient civilisations - that's the stuff of science fiction.

It 's Nothing like landing a vehicle on Mars was two hundred years ago.

We already know that there has not been an advanced civilisation on Mars, at leas, not one that left any detectable traces when the planet is viewed through the most powerful telescopes available.

Two hundred years ago men may have dreamed about going to Mars one day, they just didn't have the technology to do it. We have the technology to send a vehicle there now, but that doesn't make it any more likely that there was an advanced civilisation there. In another 200 years the situation will be the same - no advanced civilisation.

That list is often quoted when someone makes an assertive statement about the future, and I can understand why you've posted a link to it.

The reason I said what I did about an advanced civilisation on Mars - and I did qualify it by saying "not one that left any detectable traces" is because we know that such a civilisation cannot have existed without leaving traces, and we can't see any.

The other big bar to the development of life - at least beyond the level of water-dwelling microbes - is the fact that Mars lost most of its atmosphere around four billion years ago, around the same time that many scientists believe the planet was struck by a huge object, two thirds the size of our moon. This theory is based on the premise that approximately 40% of the northern hemisphere is covered by what looks like a vast impact crater measuring 10,600 km long by 8,500 km wide.

Given that Mars lost almost all its atmosphere 4 billion years ago, and the fact that the solar system was formed 4.5 billion years ago, the chances of an advanced civilisation developing before the atmosphere went, and before an impact so huge it formed the biggest crater in the solar system, is remote, to say the least.

After the impact and the loss of atmosphere conditions have been hostile to the development of any sophisticated forms of life.

I feel fairly confident, therefore, that my name will not be appearing on that list.